linux-kernel - Re: [PATCH v3] i2c: iproc: fix race between client unreg and isr

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Message-ID: <20200812200659.GA2324@kunai>
Date:   Wed, 12 Aug 2020 22:06:59 +0200
From:   Wolfram Sang <wsa@...nel.org>
To:     Dhananjay Phadke <dphadke@...ux.microsoft.com>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ray Jui <rjui@...adcom.com>,
        Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v3] i2c: iproc: fix race between client unreg and isr

On Mon, Aug 10, 2020 at 05:42:40PM -0700, Dhananjay Phadke wrote:
> When i2c client unregisters, synchronize irq before setting
> iproc_i2c->slave to NULL.
> 
> (1) disable_irq()
> (2) Mask event enable bits in control reg
> (3) Erase slave address (avoid further writes to rx fifo)
> (4) Flush tx and rx FIFOs
> (5) Clear pending event (interrupt) bits in status reg
> (6) enable_irq()
> (7) Set client pointer to NULL
> 
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000318
> 
> [  371.020421] pc : bcm_iproc_i2c_isr+0x530/0x11f0
> [  371.025098] lr : __handle_irq_event_percpu+0x6c/0x170
> [  371.030309] sp : ffff800010003e40
> [  371.033727] x29: ffff800010003e40 x28: 0000000000000060
> [  371.039206] x27: ffff800010ca9de0 x26: ffff800010f895df
> [  371.044686] x25: ffff800010f18888 x24: ffff0008f7ff3600
> [  371.050165] x23: 0000000000000003 x22: 0000000001600000
> [  371.055645] x21: ffff800010f18888 x20: 0000000001600000
> [  371.061124] x19: ffff0008f726f080 x18: 0000000000000000
> [  371.066603] x17: 0000000000000000 x16: 0000000000000000
> [  371.072082] x15: 0000000000000000 x14: 0000000000000000
> [  371.077561] x13: 0000000000000000 x12: 0000000000000001
> [  371.083040] x11: 0000000000000000 x10: 0000000000000040
> [  371.088519] x9 : ffff800010f317c8 x8 : ffff800010f317c0
> [  371.093999] x7 : ffff0008f805b3b0 x6 : 0000000000000000
> [  371.099478] x5 : ffff0008f7ff36a4 x4 : ffff8008ee43d000
> [  371.104957] x3 : 0000000000000000 x2 : ffff8000107d64c0
> [  371.110436] x1 : 00000000c00000af x0 : 0000000000000000
> 
> [  371.115916] Call trace:
> [  371.118439]  bcm_iproc_i2c_isr+0x530/0x11f0
> [  371.122754]  __handle_irq_event_percpu+0x6c/0x170
> [  371.127606]  handle_irq_event_percpu+0x34/0x88
> [  371.132189]  handle_irq_event+0x40/0x120
> [  371.136234]  handle_fasteoi_irq+0xcc/0x1a0
> [  371.140459]  generic_handle_irq+0x24/0x38
> [  371.144594]  __handle_domain_irq+0x60/0xb8
> [  371.148820]  gic_handle_irq+0xc0/0x158
> [  371.152687]  el1_irq+0xb8/0x140
> [  371.155927]  arch_cpu_idle+0x10/0x18
> [  371.159615]  do_idle+0x204/0x290
> [  371.162943]  cpu_startup_entry+0x24/0x60
> [  371.166990]  rest_init+0xb0/0xbc
> [  371.170322]  arch_call_rest_init+0xc/0x14
> [  371.174458]  start_kernel+0x404/0x430
> 
> Fixes: c245d94ed106 ("i2c: iproc: Add multi byte read-write support for slave mode")
> 
> Signed-off-by: Dhananjay Phadke <dphadke@...ux.microsoft.com>

Applied to for-next (i.e. 5.9), thanks!

BTW my code checkers found this (unrelated to this patch):

===
    CPPCHECK
drivers/i2c/busses/i2c-bcm-iproc.c:723:14: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour [shiftTooManyBitsSigned]
    val |= 1 << M_TX_WR_STATUS_SHIFT;
             ^
drivers/i2c/busses/i2c-bcm-iproc.c:741:19: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour [shiftTooManyBitsSigned]
  val = addr | (1 << M_TX_WR_STATUS_SHIFT);
                  ^
===

Use the BIT macro here.


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